“We know of at least 485 people who have drowned or are lost at sea,” Vivian Tan, spokeswoman for the UN High Commissioner for Refugees (UNHCR), said on Friday.

Tan, who described the numbers as “very worrying,” raised concern that the death toll was probably far higher.

“The fact that even women and children are increasingly risking this journey shows the growing sense of desperation among the Rohingya in Myanmar and Bangladesh,” she noted.

The Arakan Project, an NGO which supports the rights of the Rohingya, also reported a sharp rise in departures, saying over 10,000 people have ventured the perilous sea voyage since October 2012.

Chris Lewa, who heads the Arakan Project, said the estimate does not include boats leaving the Rakhine state capital, Sittwe, where tens of thousands of Rohingyas are living in camps, as her group is not able to monitor those departures.

The UN says Rohingya Muslims in Myanmar are one of the most persecuted minority groups on the planet.

Myanmar views presence of the roughly 800,000 Rohingyas in Rakhine as illegal and denies them citizenship. Thousands more live in squalid refugee camps across the border in Bangladesh.

The UN’s Tan said the latest exodus shows “the urgent need for countries in the region to respond to this humanitarian crisis by keeping their doors open to people in need of international protection from Myanmar.”

Meanwhile, Malaysia has expressed concern at the influx of refugees who see the country as the sole hope after Bangladesh closed its common border to them and Thailand as well as Singapore refused to provide asylum to the Rohingya Muslims. (T/R-015/R-006).